Pro football left me with a neck injury. Watching pro football, I mean. At least three of the games that started at 1 p.m. Eastern time on Sunday went thrillingly down to the wire, two of them bleeding into overtime, and as I sat in a sports bar jerking my gaze from the television showing the Colts to the one with the Seahawks to the one with the Rams, I suffered mild whiplash. I ache as I write.

The whole 2012 season has been like that: seesaw contests, last-minute heroics. The spectacle presented by the National Football League has perhaps never been better.

Or uglier. And on Sunday, there was also a reminder of that, the overtime games overshadowed by the anguished examination of a murder-suicide, just a day earlier, involving the Kansas City Chiefs linebacker Jovan Belcher. Belcher, 25, shot and killed his 22-year-old girlfriend, then himself. They left behind a baby girl, Zoey. Chiefs players are already talking about a fund for her. That’s apt, but they should be talking about a whole lot else as well.

There’s something rotten in the NFL, an obviously dysfunctional culture that either brings out sad, destructive behavior in its fearsome gladiators or fails to protect them and those around them from it. And while it’s too soon to say whether Belcher himself was a victim of that culture, it’s worth noting that the known facts and emerging details of his story echo themes all too familiar in pro football over recent years: domestic violence, substance abuse, erratic behavior, gun possession, bullets fired, suicide.

His death was the most stunning NFL news of the last few days, but not the only peek into a world of tortured souls and crippled bodies. In The Times, Judy Battista reported that this year would be a record one for drug suspensions in the league, a result in part of an apparent rise in the use of the stimulant Adderall. The record could reflect heightened vigilance by league officials, but still: The high stakes, physical demands and physical agony inherent in pro football indisputably encourage drug taking, and some oft-medicated players graduate to years of addiction problems.

The scientific journal Brain just published a study by Boston University investigators of 85 people who had received repeated hits to their heads while they were alive and were examined posthumously for degenerative brain disease. Sixty-eight of those people had such disease, which can lead to mood swings, dementia, depression. Fifty of them had played football, 33 in the NFL, including Dave Duerson, the former Chicago Bears safety who shot himself fatally in the chest last year after sending his ex-wife a text message requesting that his brain tissue be analyzed for football-related damage.

The study’s publication follows the consolidation this year of more than 100 lawsuits involving more than 3,000 former NFL players and their families, who accuse the league and its official helmet maker of hiding information about the relationship between injuries on the field and brain damage. It also follows the revelation this year that the New Orleans Saints engaged in a bounty program by which defensive players got extra money for knocking opponents out of games.

In May the former San Diego Chargers linebacker Junior Seau, a veritable legend whom I’d known for years as Nemesis No. 1 of my beloved Denver Broncos, shot and killed himself, and in a heartbreaking assessment of his demise five months later, the San Diego Union-Tribune noted that “within two years of retiring, three out of four NFL players will be one or more of the following: alcohol or drug addicted; divorced; or financially distressed/bankrupt. Junior Seau was all three.”

In the same article, the newspaper reported that the suicide rate for men who have played in the NFL is nearly six times the national average.

The Union-Tribune maintains a database of NFL players arrested since 2000. The list is long, and the league is lousy with criminal activity so varied it defies belief. The quarterback Michael Vick of course staged inhumane dog fights; the wide receiver Plaxico Burress accidentally shot himself in the leg with a gun he’d toted illegally into a nightclub; the wide receiver Dez Bryant was accused of assaulting his own mother.

How all of this misfortune and all of these misdeeds do and don’t relate to one another isn’t clear. But to be an NFL fan these days is to feel morally conflicted, even morally compromised, because you’re supporting something that corrodes too many lives.

The Chiefs quarterback Brady Quinn said Sunday that Belcher’s bloody end left him wondering “what I could have done differently.” That’s a question that everyone in the NFL should mull.

And we fans must demand it. On Monday morning, what didn’t feel right wasn’t just my neck, but also my conscience.